Answer:
[tex]1.94\times10^{-3}[/tex] m
Explanation:
Condition for constructive interference is
[tex]y =\frac{m\lambda}{d} D[/tex]
y= width of the first bright fringe
λ= wavelength of the incident light
d= distance between the slits
D= distance of the screen from the slit
for first order 1st wavelength
[tex]y_1 =\frac{1\times660\times10^{-9}}{0.49\times10^{-3}} 5[/tex]
[tex]y_1=6.73\times10^{-3} m[/tex]
Now, for first order 2nd wavelength
[tex]y_2 =\frac{1\times470\times10^{-9}}{0.49\times10^{-3}} 5[/tex]
[tex]y_2=4.79\times10^{-3} m[/tex]
The distance between the first bright fringe for each wavelength
[tex]d=y_1-y_2\\=(6.73-4.79)\times10^{-3} m\\=1.94\times10^{-3} m[/tex]
